In modern supermarkets and in handling of foodstuff packages generally, increasing use is being made of so-called "bar codes", universal product codes (UPC) or EAN codes to identify the product, facilitate checkout and inventorying and to simplify the handling of the packages.
When foodstuffs such as eggs are provided in packages, it is possible to close the bottom of the package by a planar cover. While this may provide good visibility of the product, especially if the cover is transparent, it poses a problem if the bar code is to be applied to the planar upper surface since the passage of the package across the bar code reading will require that the package be turned over, an operation which may be detrimental to the contents.
The cover could, of course, be of the fitted type and provided with the code on a lateral susrface. Such fitted covers, however, are comparatively costly, difficult to position quickly and pose problems with respect to securing and removal.